[PATCH] drm/amdgpu: zero reg_state buffer before filling it

[Dmitriy Chumachenko <Dmitry.Chumachenko@cyberprotect.ru>]

The reg_state readouts return szbuf bytes but never write the pad members  
of the headers and of amdgpu_smn_reg_data (and, for pcie, the fields       
skipped when the upstream port or AER capability is absent). The sysfs     
buffer is a plain kmalloc(), so those bytes leak stale slab data to any    
local user through the 0444 reg_state attribute.                    
                                                                           
Zero the buffer once the size is known.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 081a6eda2b25 ("drm/amdgpu: Read aquavanjaram PCIE register state")
Signed-off-by: Dmitriy Chumachenko <Dmitry.Chumachenko@cyberprotect.ru>
---
 drivers/gpu/drm/amd/amdgpu/aqua_vanjaram.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/aqua_vanjaram.c b/drivers/gpu/drm/amd/amdgpu/aqua_vanjaram.c
index 72ea37dbfea8..0086de0f685d 100644
--- a/drivers/gpu/drm/amd/amdgpu/aqua_vanjaram.c
+++ b/drivers/gpu/drm/amd/amdgpu/aqua_vanjaram.c
@@ -610,6 +610,8 @@ static ssize_t aqua_vanjaram_read_pcie_state(struct amdgpu_device *adev,
 	if (max_size < szbuf)
 		return -EOVERFLOW;
 
+	memset(buf, 0, szbuf);
+
 	pcie_regs = (struct amdgpu_regs_pcie_v1_0 *)((uint8_t *)buf +
 						     sizeof(*pcie_reg_state));
 	pcie_regs->inst_header.instance = 0;
@@ -702,6 +704,8 @@ static ssize_t aqua_vanjaram_read_xgmi_state(struct amdgpu_device *adev,
 	if (max_size < szbuf)
 		return -EOVERFLOW;
 
+	memset(buf, 0, szbuf);
+
 	p = &xgmi_reg_state->xgmi_state_regs[0];
 	for_each_inst(i, adev->aid_mask) {
 		for (j = 0; j < xgmi_inst; ++j) {
@@ -776,6 +780,8 @@ static ssize_t aqua_vanjaram_read_wafl_state(struct amdgpu_device *adev,
 	if (max_size < szbuf)
 		return -EOVERFLOW;
 
+	memset(buf, 0, szbuf);
+
 	p = &wafl_reg_state->wafl_state_regs[0];
 	for_each_inst(i, adev->aid_mask) {
 		for (j = 0; j < wafl_inst; ++j) {
@@ -902,6 +908,8 @@ static ssize_t aqua_vanjaram_read_usr_state(struct amdgpu_device *adev,
 	if (max_size < szbuf)
 		return -EOVERFLOW;
 
+	memset(buf, 0, szbuf);
+
 	p = &usr_reg_state->usr_state_regs[0];
 	for_each_inst(i, adev->aid_mask) {
 		usr_regs = (struct amdgpu_regs_usr_v1_0 *)p;
-- 
2.49.0